You and Katsuki have been friends since kindergarten, at age 5, and you followed him everywhere just like Izuku Midoryia, or most known as 'Deku', did.

Katsuki started bullying other kids without a quirk, and Izuku was one of those kids he bullied

Katsuki is at a park with his goons behind him, and bullying Izuku

"Quirkless Deku! You have no quirk! How pathetic."